This invention is in the field of rotary exchangers for gas turbine installations, in particular a modular exchanger entity and its sealing devices.
For a long time, means have been sought for the reduction of fuel consumption in gas turbine installations by recovering heat from the exhaust gases. Numerous types of exchangers have been tested and used. A stationary installation does not raise problems, which are too complicated and does not require the use of exchangers with light weight and small dimensions, it is not the same for mobile installations, in particular aircraft turbines.
French Pat. No. 1,496,850 provides a solution for the use of exchangers for the recovery of heat from the combustion gases in an aircraft turbine. In these exchangers, the hot combustion gases and the compressed cold air coming from the compressor are simultaneously passed through the same heat exchanger paths. Inside of the exchanger tubes, in a first step, the heat of the hot gases is absorbed and then, in a second step, it is given off to the colder compressed air coming from the compressor and feeding the combustion chamber. A distribution system of the hot gases and of the cold air is disposed in front of the ends of the exchanger tubes, carried by a rotary drum. By means of rotation, the tubes are successively located in front of each of the distributors and thus permit their successive sweeping by the hot gases and by the hot air. The temperature of the exhaust gases extends through a temperature range of 550.degree. to 850.degree., the rotating elements are subjected to significant temperature variations, which have the effect of a change in their geometrical dimension. The patent, which is mentioned below, succeeds in limiting this variation by circulating the cold air in the support components of the stationary parts and of the rotating parts of the exchanger. These supports form a part of the compressed air feed piping. The exchanger matrices are comprised of tubes which are maintained between two annular supports. The exchanger tubes are fixed to only one of their ends, the other end being freely slidable in the support. The gases are piped through the entire length of the exchanger tubes by resilient elements, which are fixed at their ends to the end supports of the rotor and which can move freely.
The measures taken for limiting the longitudinal variations of the rotor must be accomplished by a reduction of leakage; leakages occur principally at the transitions or joints of the compressed air piping of the fixed support to the exchanger tubes of the rotating support. In fact, the pressure of the air is very much greater than that of the hot gases and it tends to leak either towards the flow of hot gases or into the atmosphere. When the rotor turns, a certain quantity of compressed air is isolated in the passages and escapes in the hot gases, which comprises a loss by entrainment.
The repetition of this loss of compressed air quite seriously comprises the energy savings which can be expected from an exchanger system. French Pat. No. 1,497,700 indicates means, which permit the reduction of these losses. To accomplish this, each end of the rotor has sealing means comprised of joint plates, which are radially disposed and extend over one portion of the upper circumference to the circumferential portion occupied by the collector taking or recovering the fluid going through the heat exchanger matrices. The rotor has fixed inside and outside annular joints (with respect to the crown of the exchangers), which cooperate with similar joints on the fixed portion. These joints are formed of annular segments, which are resiliently urged in the axial direction and towards the rotor joint by springs. The sealing device prevents radial losses. The circumferential losses between the high pressure (compressed air) and low pressure (exhaust gas) components are avoided by the use of two joint plates, which are disposed at the ends of the fluid collector, radially extending from the inside annular joint to the outside annular joint, going past the ends of the collector. These plates have grooves into which T-section bars are placed. These bars, of which the middle bar of the T cooperates with the plane surfaces of the joint elements, which are disposed between the adjacent pairs of heat exchanger conduit, assure tightness. The distance separating two lines of bars is less than the size of the joint elements, which are disposed between the exchange conduits. Pipe connections connect the two joint plates in order to equalize the pressure between the low pressure (exhaust gas) and the high pressure (compressed air) conduit.